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Vulnerability record · CVE-2017-18342 · published 27 June 2018

CVE-2017-18342: Pyyaml deserialization of untrusted data vulnerability

Pyyaml · Pyyaml

In PyYAML before 5.1, the yaml.load() API could execute arbitrary code if used with untrusted data. The load() function has been deprecated in version 5.1 and the 'UnsafeLoader' has been introduced for backward compatibility with the function.

9.8 CVSS 3.1 Critical EPSS 5.7% · top 7.3% CWE-502 · Deserialization of untrusted data
9.8CVSS 3.1 base score, v2 7.5
5.7%EPSS exploitation probability, 30 days
NoNot in CISA KEV
2Affected product versions listed by NVD
18References
17 Jun 2026Last modified by NVD

Description

In PyYAML before 5.1, the yaml.load() API could execute arbitrary code if used with untrusted data. The load() function has been deprecated in version 5.1 and the 'UnsafeLoader' has been introduced for backward compatibility with the function.

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected products

2 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://github.com/marshmallow-code/apispec/issues/278 Third Party Advisory
https://github.com/yaml/pyyaml/blob/master/CHANGES Release NotesThird Party Advisory
https://github.com/yaml/pyyaml/issues/193 Third Party Advisory
https://github.com/yaml/pyyaml/pull/74 PatchThird Party Advisory
https://github.com/yaml/pyyaml/wiki/PyYAML-yaml.load%28input%29-Deprecation
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/JEX7IPV5P2QJITAMA5Z63GQ
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/KSQQMRUQSXBSUXLCRD3TSZY
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/M6JCFGEIEOFMWWIXGHSELMK
https://security.gentoo.org/glsa/202003-45 Third Party Advisory
https://github.com/marshmallow-code/apispec/issues/278 Third Party Advisory
https://github.com/yaml/pyyaml/blob/master/CHANGES Release NotesThird Party Advisory
https://github.com/yaml/pyyaml/issues/193 Third Party Advisory
https://github.com/yaml/pyyaml/pull/74 PatchThird Party Advisory
https://github.com/yaml/pyyaml/wiki/PyYAML-yaml.load%28input%29-Deprecation
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/JEX7IPV5P2QJITAMA5Z63GQ
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/KSQQMRUQSXBSUXLCRD3TSZY
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/M6JCFGEIEOFMWWIXGHSELMK
https://security.gentoo.org/glsa/202003-45 Third Party Advisory

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Source: NIST National Vulnerability Database (record CVE-2017-18342), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.